The objectives of the study are to determine how particulate matter which reaches the alveolar surface affects the potential lung defense functions of alveolar macrophages. The study involves: (1) utilization of in vitro cultures of alveolar macrophages so as to isolate the activity of these cells from other lung defense mechanisms; (2) examination of the processes by which macrophages incorporate particles; (3) studying the means by which inert particles might block or partially block alveolar macrophages and the consequences of such a block in both immunologically specific and non-specific areas. The process of particle handling has been broken down for study into three general sections: (1) interaction of particles with the membrane and resultant vesiculation; (2) interaction of particles with artificial membranes and the effects on phase transition; (3) regurgitation or exocytosis of enzymes potentially inimical to the integrity of pulmonary tissue; (4) intracellular transport of particles and coalescense with lysosomal organelles.